1. Field of the invention
The present invention relates to sunshields, and specifically to automobile sunshields for blocking sun rays and inhibiting heat transfer through the window of a parked automobile.
2. Description of Prior Art
The problem of temperature build up inside a car parked in the sun is well recognized. Not only that this causes extreme discomfort to the driver and passengers upon their returning, it also adds more load to the air conditioner and destroys the plastic, fabric, and other materials within the vehicle.
Numerous vehicular sunshields have been introduced into the market to solve this problem. Broadly speaking, they fall into two main categories: out-door and in-door. The out-door devices include a cover to cover the entire car. This is very bulky and using it is very time-consuming and awkward. It is therefore less preferable to those in-door means such as curtains or venetian blinds or folding cardboard.
The design of an indoor sunshield, hereafter referred to simply as sunshield, must take into consideration at least the following problems:
(1) Storage: If the sunshield is not fixed permanently in the car, when not in use, it must be compact for storage; if it is, then it must be stored in a suitable position unobstructive to the normal usage of the car when not in use.
(2) Coverage: In use against the window, the sunshield must cover it as much as possible, leaving no "holes" so that sun rays can pass through.
(3) Ease of positioning: The driver must be able to position the sunshield against the window with ease. Ideally, the movement of the sunshield from its storage position to its operative position against the window must be fixed so that an electrical device can be installed to move it back and forth between these positions upon the turn of a switch.
(4) Insulation: The sunshield must be made of suitable material to reflect the sunlight and to prevent heat transfer to inside the car.
(5) Economy: Not only that the sunshield must not be too expensive to produce, it must last for a long time, preferably for the lifetime of the vehicle.
(6) Appearance: The sunshield must be pleasant looking, blending nicely with the design and color of the car. It cannot distort material printed on it, making it hard to read.
Prior art sunshields have not been able to address all these problems satisfactorily. As an example, let us consider U.S. Pat. No. 4,202,396 to A. Levy (1980), which is currently the most successful commercially. It is made of cardboard, folded in an accordion fashion. In folded mode, it is too bulky for storage. In operative mode, it does not conform to the contour of the window, thus is unable to cover it completely. Positioning it to the window is not a simple task. It is relatively cheap, because it uses cheap material. This, however, results in inferior heat resistance and, coupled with the drying effect of the elevated temperature and the constant folding between the joint sections, in rapid deterioration. Even when it is new, its folded surface makes messages or designs printed on it hard to read; when it is old and torn, it is unsightly. Other type of sunshields include those fan-like venetian blinds as shown in Surtin, U.S. Pat. No. 4,332,414 (1982). These sunshields cannot cover the window enough to make it effective. Sunshields using curtains might be able to cover the window better, but are too complicated to operate.
It is therefore highly desirable to provide a sunshield which can address all these above problems satisfactorily.